Electric Generator Design Project

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Electric Generator Design Project ReportOctober 26, 2009

The InnovatorsMatt DalrympleTravis Watson

Jonathan Schworer


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The objective of this project was to create a device that demonstrates to students inmiddle school how to convert mechanical energy to electrical energy. We designed our generatorwith a fishing reel connected to a metal shaft connected to an acrylic disk with magnets attachedso the disk would spin the magnets past coils of wire to light up a red LED. When the fishingreel handle is turned at a quick but reasonable pace, the red LED blinks brightly. This indicated

that we have successfully converted mechanical energy into electrical energy. The design may befurther improved by replacing the fishing reel with an acrylic gear set, allowing the project to bereplicated more easily.

ContentsIntroduction ..................................................................................................................................... 3

Design Procedure ............................................................................................................................ 3

Problem Definition...................................................................................................................... 3

Constraints and Criteria .............................................................................................................. 3Research ...................................................................................................................................... 4

Alternative Solutions .................................................................................................................. 4

Analysis....................................................................................................................................... 5

Decision ...................................................................................................................................... 6

Specifications .................................................................................................................................. 6

Bill of Materials .......................................................................................................................... 6

Fabrication instructions ............................................................................................................... 6

Assembly Instructions ................................................................................................................. 6

Recommendations and Conclusions ............................................................................................... 7

Appendix ......................................................................................................................................... 9

CAD Drawings............................................................................................................................ 9


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IntroductionIt was our goal in this project to create a generator, which is defined as a device that

converts mechanical energy to electrical energy. Not only did we want to create a generator, butcreate one that is simple enough that students in middle school can grasp the concept of how itworks. After some trial and error, as well as further refinement after we had it working, we

developed a smooth and simple to operate device. The following report details, in order of theOakes text design process, what we were up against and how we arrived at our final design.

Design Procedure

Problem DefinitionThe process of using electromagnetism to create electricity has been around for a long

time and is widely used, so the problem is creating a device that demonstrates the process tostudents in middle school. In order for them to grasp the concept, it has to be simple. Also, withtheir typically short attention spans, it has to be somewhat unique and interesting. We needed towork within our limited amount of electromagnetism knowledge, keep the overall cost fairlylow, and come up with an operable device in a relatively short period of time.

PROBLEM STATEMENT: Create a device that demonstrates to students in middleschool how to convert mechanical energy to electrical energy.

Constraints and CriteriaCONSTRAINTS-Show mechanical energy being converted to electrical energy-Operable by students in middle school-Safe for students in middle school-Overall size no larger than 1’H x 1’W x 2’L

CRITERIA-Simple-Appeals to boys and girls-Durable-Draws and keeps students attention-Cost effective

We chose our constraints because they are the major needs involved. It did not matterhow the conversion process was shown, but it had to be designed so students in middle schoolcould figure out how to use it without hurting themselves or each other. We also had to limit theoverall size of our device so it can be placed in the display cases at Sanford Middle School.

Our criteria also contribute to a final product that will give the students a clear lesson inelectromagnetism and power production. It is important for the device to be simple because ourtarget audience has little to no previous knowledge of how mechanical energy is converted toelectrical energy. We do not want them to get overwhelmed. While engineering has traditionally been a male dominated field, there are both boys and girls in our target audience, so it needs toappeal to both. Durability is a concern because students in middle school are not typically knownfor being gentle with things. We can visualize them pulling the devices away from one anotherand pushing the devices to their limits to see who can create the most power. To teach them a


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lesson on what they may consider a boring topic, the device needs to catch their attention andhold it long enough for them to understand how it works. Finally, since we are all students onlimited budgets, the model needed to be fairly cheap.

ResearchEarly on in this project, we were given a lecture on electromagnetism. We knew that one

of the best ways to reproduce this was passing magnets by a fixed coil of wire. We also knewthat an LED was one of the simplest ways to show that this power was being produced. Prior togetting an LED from the lab, we tried hooking up both 12V and 6V halogen bulbs to our device but neither showed any signs of illuminating. Because there are so many colors of LEDs tochoose from, we decided it would be a good idea to find out if different colors required differentvoltage to light up. Based on the website www.theledlight.com, non-high-brightness red requiresonly 1.7 volts; whereas, high-brightness red needs 1.9V, orange and yellow need 2V, and greenneeds 2.1V. Whites and blues require even more. Since we didn’t know how much voltage wewould be able to produce, we decided to use a single red LED as our diode/power indicator.

We also learned that a diode only allows current to flow in one direction. Therefore,without a rectifier, the LED would flicker. We decided, in the interest of simplicity and holdingstudents’ attention, that we would omit the rectifier.

Beyond learning about the LEDs and rectifiers, it was mostly a matter of trial and errorwith coil to magnet orientation, speed of the magnets, number of magnets, number of coils, andsize of the coils.

Alternative SolutionsAlternative #1 (Figure 1) One of our early designs consisted of magnets fixed to a shaft

with a hand crank on the end of the shaft. When the crank was turned, the magnets would rotateinside a large, fixed coil of wire. The wire leads (ends) would be connected to an LED. All the

components would be mounted on a wood frame.Alternative #2 (Figure 2) Another one of our ideas was to build a small box,

approximately 6”x6”x2”, and mount the magnets on a shaft that passed through the box. A crankwould be attached to one end of the shaft to make turning the shaft easier. Wrapping magnet wirearound the box would then serve as the coil. Similar to our previous design, the wire leads wouldhave connected to an LED, which also would have been mounted to the box in some fashion.

Alternative #3 (Figure 3) Our third alternative involved a horizontal shaft passingthrough and supported by two wood mounts. On the end would be a bracket, shaped like a threedimensional fork, with a magnet attached at the end of each prong. A coil would then have beensuspended between the fork prongs so the magnets would rotate around the coil as the shaft wasturned. Similar to the others, the wire leads would be directly connected to an LED.


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AnalysisAlternative #1 (Figure 1) Our first design was simple. There were no hidden parts or

extra parts cluttering it up. There was only one coil and no gears. As far as appealing to boysand girls, this design was boring and had basically no special appeal to either gender. With a lownumber of moving parts, it would have been durable. As long as the shaft mounts were solid, the

crank would have been about the only thing that could have broken. It also would have been costeffective, with a minimal amount of wood for the base, only one bulb, one coil of wire, and twomagnets.

We scrapped this idea early on, however, because of the orientation/rotation of themagnets relative to the coil. The magnets would have rotated parallel to the coil and inside it.Therefore, the magnetic fields would not have cut across the coil, and least not completely.Because of that, little to no voltage would have been induced into the coil. Even if the orientationof the coil to magnets was corrected, this design likely would have required exposed gears togenerate enough power.

Alternative #2 (Figure 2) Our second design was even simpler than our first. Like the

first, it contained magnets on a shaft spinning past a coil and inducing voltage to illuminate anLED. The major differences were the coil-to-magnet orientation and the construction of the baseframe. The main durability issue we saw with this design was keeping the magnets centered sothey didn’t rub the sides of the box as the crank was turned. The LED was also a concern. Withthis compact layout, the LED likely would have had to be outside the frame, where it could beeasily broken. Like the first, this model would have had no specific appeal to boys or girls andwas somewhat boring. Of the three alternatives and the final product, this would have been thecheapest to build.

We liked the simplicity of this design, but were concerned with generating enoughvoltage. The shaft can only be turned so fast with a human cranking at a 1:1 ratio. Affixing gearsto this setup would have made it quite cumbersome. We felt more confident with the coil-to-

magnet orientation here, but we didn’t feel that the strongest parts of the magnetic field would beclose enough to the coil, especially using the FabLab provided magnets.

Alternative#3 (Figure 3) For our third design, we went back to a larger platform. Wewanted to be able to adapt gears if necessary. Simplicity was on par with the others, butdurability was slightly less. The four prongs of the fork, which were to be made of wood, wouldhave been liable to break if bumped against something. Appeal to the students likely would have been a little better because there would have been more movement. The fork containing themagnets would spin, rather than just the shaft with the magnets directly attached as inAlternatives #1 and #2 (Figures 1 and 2). As far as cost, this design would be very similar toAlternative #1 (Figure 1) because they contain almost identical components, just with a different

layout. The primary reason we rejected this one was the durability issue with the prongs of thefork. We also realized at this point that the best way to orient the magnets and coils was face toface. We liked the rotating shaft and base setup, but also realized the need for the shaft to rotatefaster and more smoothly to generate enough speed to light the LED.


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DecisionThe design that we agreed upon was a modified version of Alternative#3 (Figure 3). We

came to this decision with the use of the decision matrix in Figure 9. Instead of having a prongedfork as a base for the magnets, we opted to glue the magnets to a disk of acrylic. To orient thecoils of wire in a way that would produce electricity, we mounted the coils on a vertical piece of

wood, and placed it as close as possible to the magnets without touching them.Our final design was a solution to the problems with Alternative#3 (Figure 3). The diskwas simpler than the pronged fork. It was also more durable. This design would also keep thestudents’ attention better because a simple disk does not hide parts of the design like the prongedfork would.

Specifications

Bill of Materials

½” plywood $6.971”x6”x6’ pine board $3.24 Snoopy fishing pole $9.991 5/8” wood screws (8) $0.25 1’ ¼” dia. Steel rod $0.50 Locking collars (2) $5.00Magnet wire (3100ft spool) $19.95Magnets (4) $8.20LED (1) $0.30¼” nuts (2) $0.24 Acrylic (4” dia. Circle) $2.00 Zip ties (12) $0.60 Nylon bushings (2) $4.00

TOTAL COST $61.24

Fabrication instructionsCut out the three pieces of the shaft support and the coil plate (Figure 6) out of ¾” wood,

including one support top (Figure 4) and two support sides (Figure 5). Out of the plywood, cut a1’x18” piece to be your base. Use a laser cutter to cut a 4” diameter disk of acrylic, with a hole inthe center just slightly smaller then ¼” diameter.

Assembly InstructionsThe base for our end product is similar to Alternative #3 (Figure 3). Use the three piece

shaft support, made of ¾” wood, and mount it to a ½” plywood base using screws. Insert thenylon bushings into the upper horizontal holes of the support sides (Figure 5). A ¼” steel rod,threaded at both ends is then mounted in the shaft support. Insert the fishing rod into the lowerhorizontal holes of the support sides (Figure 5). Attach locking collars on either side of the shaft


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and more magnets. However, in the interest of simplicity, we decided it was only necessary tocreate enough voltage to power one LED. Again, our goal was primarily to show the conversionof mechanical energy into electrical energy, so once we could light the LED, we did not do anyfurther refinement beyond making it operate more smoothly. Research could be done on theorientation of the magnets, the number of coils, methods of interconnecting coils, and connecting

multiple LEDs. This further research was simply not necessary, and a more advanced setup mayhave been a detriment to the goal of this project.


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Appendix

CAD Drawings

Figure 1 Alternative #1



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Figure 4 Support Top


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Figure 5 Support Sides

Figure 6 Coil Plate


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Figure 7 Completed Support And Shaft Without Fishing Reel


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Figure 8 Completed Support And Shaft Without Fishing Reel

Figure 9 Decision MatrixSimplicity20%

Boy and Girl Appeal10%

Durability25%

Attention Getting40%

Cost5% To

Alternative #1 7 5 6 4 8



ChosenDesign 6 6 6 9 6

Documents

Electric Generator Design Project